Process for making delayed petroleum coke

ABSTRACT

A method of making quality coke having improved uniformity is obtained by coking a high boiling hydrocarbon in the presence of a halogen, a hydrogen halide or a hydrocarbyl halide under delayed coking conditions comprising a temperature from 800* to 1200* F. and a pressure from 1 to 10 atmospheres and sufficient to convert the coking feedstock to vapors and dry coke.

United States Patent lnventor Hillis 0. Folkins Claremont, Calif.

Appl. No. 29,070

Filed Apr. 16, 1970 Patented Nov. 9, 1971 Assignee PROCESS FOR MAKING DELAYED PETROLEUM COKE 10 Claims, 1 Drawing Fig.

US. Cl

208/46, 208/125 lnLCl .1 C10g9/l4 Field of Search .1

Union Oil Company of California Los Angeles, Calif.

[56] References Cited UNITED STATES PATENTS 2,984,618 5/1961 Edelman et a1. 208/127 3,226,316 12/1965 Metrailer et a1.. 208/127 3,347,776 10/1967 Mitchell et al. 208/46 Primary ExaminerHerbert Levine Attorneys-Milton W. Lee, Richard C. Hartman, Lannas S.

Henderson, Dean Sandford and Robert E. Strauss ABSTRACT: A method of making quality coke having improved uniformity is obtained by coking a high boiling hydrocarbon in the presence of a halogen, a hydrogen halide or a hydrocarbyl halide under delayed coking conditions comprising a temperature from 800 to 1200 F. and a pressure from 1 to 10 atmospheres and sufficient to convert the coking feedstock to vapors and dry coke.

PROCESS FOR MAKING DELAYED PETROLEUM COKE DESCRIPTION OF THE INVENTION This invention relates to a process for producing coke, and more particularly to a process for making high quality coke from delayed coking procedures.

In the production of coke by delayed coking processes, a stream of high boiling hydrocarbons is heated to cracking temperatures and continuously fed into the bottom of a coking drum. In the drum the preheated hydrocarbons are allowed to soak in their own heat which is sufficient to convert the hydrocarbons to dry coke and cracked vapors, the latter being continuously removed overhead and sent to a fractionating column, while the coke accumulates to successively higher levels in the drum. When the drum is filled with coke, the heated coking feedstock is diverted to another drum and the filled drum is steamed and cooled and the coke is removed therefrom by hydraulic jets of water or other means.

The coke which accumulates in the coking drum has a volatile combustible material content which varies considerably with the position of the coke in the drum. As the coke successively builds up in the drum, the coke in the lowermost part of the drum is subjected to the preheated hydrocarbon feed for a longer period of time than the upper levels of coke. This prolonged contact with the preheated feed reduces the amount of volatile combustible material in the coke and results in a coke having a varying volatile combustible material content throughout the coking drum. This nonuniformity in processing is often sufficient to cause the volatile combustible material content of the coke at the bottom of the drum to be from l to 20 weight percent less than the volatile combustible material content of the coke at the top of the drum.

The quality of the coke product is controlled to a large extent by the amount and uniformity of the volatile combustible materials in the coke. For example, it has been found that cokes having nonuniform volatile combustible material contents which vary more than weight percent, or cokes having average volatile combustible material contents greater than about weight percent or less than 8 weight percent are undesirable for most commercial processes.

Attempts to correct the nonuniformity of the volatile combustible material contents of cokes or to adjust their average volatile combustible material contents to the desired range by adjustment of the delayed coking process variables have not been fully successful. For example, the economic value of the distillates obtained by fractionation of the vapors from the coking process usually far exceeds the value of quality coke and, consequently, coke quality and uniformity is placed in a secondary position. Thus the cokers are operated at process conditions which will produce a high or otherwise good yield of distillates fuels which are recovered from the overhead vapors of the coking unit without consideration of conditions that would yield quality coke products.

More recently, however, coke is assuming a more important role in the chemical industry and high quality cokes are commanding premium prices according to the specific end uses to which they are directed. Accordingly, a need exists for an improved cokjng process wherein high quality coke having a substantially uniform volatile combustible material content is obtained without reducing the high distillate fuel yields from the coker unit.

it is, therefore, an object of this invention to provide an improved coking process.

It is another object of this invention to provide a method of producing a high quality coke.

It is also an object of this invention to provide a process for producing high quality coke having a substantially uniform volatile combustible material content.

It is still another object of this invention to provide a process for producing coke having a substantially uniform volatile combustible material content without reducing the yield of distillate fuels from the coking unit.

Other and related objects will become apparent to those skilled in the art from the following description of the invention and the attached drawings.

The above objects and attendant advantages can be attained by introducing a small amount of a halogen, hydrogen halide or a hydrocarbyl halide into the coking drum during the coking operation. The invention is applicable to conventional coking processes such as previously described where the preheated feedstock is introduced into the bottom of a drum and permitted to reduce to vapors and dry coke by its contained heat. Supplemental heating of the coking vessel can also be employed if desired, e.g., by direct firing of the outside vessel walls or by introducing a vapor or gas such as a hydrocarbon gas or inert gas, e.g., nitrogen, preheated to the coking temperature, into the coking drum.

It has been found that the presence of one of these halogen containing compounds improves the volatile combustible material uniformity of the coke throughout the coking drum without substantially affecting the coking operating conditions. Thus, by introducing this halogen compound into the coking drum, the operating conditions can be conveniently maintained at the optimum value for distillate fuels production while an appreciable conversion to coke having a uniform volatile combustible material content can be realized.

The improvement in the volatile combustible material uniformity of the coke can be readily observed from the graph presented in the attached drawing. As illustrated in the drawing, the line connecting points A, B and C represents the volatile combustible material content of a coke throughout the coker drum in a conventional delayed coking process. A vertical line would depict complete or ideally uniform coke having no variation in volatile combustible material. The shaded area under line ABC, therefore, illustrates the extent of the coke nonuniformity and the larger the shaded area the greater is the nonuniformity of the coke. The line connecting points A,, B and C represents the volatile combustible material content of a coke produced in an identical coking drum with the same feed and under the same delayed coking conditions except that a minor amount of a hydrocarbonyl halide is introduced into the coking drum. lt can readily be seen that the shaded area under line A,B,C, is considerably less than the area under line ABC and therefore illustrates a coke having enhanced uniformity. The addition of free halogen or a hydrogen halide to the coking unit results in a similar reduction of the nonuniformity as illustrated in the drawing. The coking conditions and the hydrocarbyl halide employed in obtaining the data represented in the drawing is presented in example 1.

Halogen containing compounds which an be employed in accordance with this invention comprise halogens, hydrogen halides or hydrocarbyl halides having from one to about 20 carbon atoms. Suitable hydrocarbyl halides include saturated aliphatic halides having from one to 20 carbon atoms, exemplary of which include: bromomethane, tribromomethane, chlorobromomethane, dibromomethane, fluoromethane, l,ldibromoethane, l,2-dibromoethane, 1,1-chlorobromoethane, l,2-chlorobromoethane, l,2-dibromopropane, 1,3- dibromopropane, 1,3-difluoropropane, 1,3-dichloro-npropane, l,3-dibromo-2-methylpropane, l,2-dibromobutane, l ,2-dichloro-n-butane, l,2-diiodobutane, l,2-dibrornopentane l,l-dichloro-3-bromopentane, l,2-dibromo-3-methylpentane, l,2-dibromohexane, l,2dichloro-n-heptane, 1,2,6- tribromoundecane, l,2-dibromo-4,5-diethyltridecane, l,2- dibromoeicosane, etc.; unsaturated aliphatic halides having from two to about 20 carbon atoms, exemplary of which include bromoethene, l,2dibromethene, l-chloro-2- bromoethene, l,2-dichloroetliene, l, l -dichloro-2- bromoethene, tribromoethene, l,2-dibromopropene-2, l

bromo 3-iodopropene- 2,l-bromopropene-2, l-bromo-lmethylethene, l,2-dichlorobutene-2, l,2-dibromobutene-2, l,3-dibromo-l-chlorobutene-2, l,2-dibromopentene-3, l,2- dichlorooctene-4, l,2-dibromooctene-2, 1,5-dibromo-3 ,4- dichlorononene-S, 1,2, 2-dibromoundecene-5, l-bromo-Z- methylpentadecene-S, etc., alicyclic halides having from three to about 20 carbon atoms, exemplary of which include bromocyclopropane, dibromocyclopropane, trichlorocyclopropane, bromocyclobutene, 1,2-dibromocyclobutane, tribromocyclobutane, 1,2-dibromocyclopentane, 1,3 -dichlorocyclopentane, 1,2-dibromo-3-ethylcyclopentane, 1,2- dichloro-3-amylcyclobutane, 1,2,3 -tribrornocyclohexane, 1,2- dibromocyclohexane, hexabromocyclohexane, 1,2-dibromo- 4-octylcyclohexane, etc., aromatic halides having from six to about 20 carbon atoms exemplary of which include bromobenzene, l,2-bromobenzene, 1,2,4-tribromobenzene, chlorobenzene, 1,2-dichlorobenzene, iodobenzene, 1,2- diiodobenzene, l,2-dibromo-3-methylbenzene, 1,2-dibromo- 3 ,4-diethyl-5methylbenzene, hexachlorobenzene, 1,3- dibromo-2-propylbenzcne, 3-chloro-5-iodo-l -isobutylbenzene, l,3-dibromo-2,4, -diethylbenzene, 1,2- dibromonaphthalene, 1,3-dibromonaphthalene, 1,2- dichloronaphthalene, 1,4-dichloronaphthalene, 1-bromo-2- methylnaphthalene, etc.

Suitable halogens which can be employed herein include fluorine, chlorine, bromine and iodine. Suitable hydrogen halides which can be employed include hydrogen chloride, hydrogen bromide and hydrogen iodide. Since the free halogens and the hydrogen halides are normally corrosive to the metallic surfaces of the coking drum at conventional coking temperatures, it is preferred that the hydrocarbyl halides and, more preferably, that the hydrocarbyl bromides or chlorides be employed.

The halogen, hydrogen halide or hydrocarbyl halide additive can be introduced into the coking drum by admixing it with the coker oil feed and thereafter heating and injecting the mixture into the bottom of the coking drum, or alternatively, the additive component can be injected directly into the coker drum during coking. In one specific embodiment the additive is injected into the coker drum at several drum elevations so that as the coke gradually builds up in the drum the additive may be injected into the liquid pool of soaking hydrocarbons in the drum at progressively higher locations.

Usually, however, the most convenient method of introducing the additive into 87is by dissolving or dispersing the halogen, hydrogen halide or hydrocarbyl halide in the coker feedstock. The resulting mixture can then be heated to coking temperatures and injected into the bottom of the coking drum. It is also preferred that the additive be continuously introduced into the feedstock or coking drum so that a uniform coke quality can be maintained.

The halogen, hydrogen halide or hydrocarbyl halide additive may be a solid, liquid or gas, depending on the injection technique employed and the injection temperature. In instances where the additive is introduced directly into the coking drum it is preferred to heat the additive up to the temperature existing in the coking drum. At these high temperatures the additive component is a gas, and accordingly, the gaseous additive can be injected into the coking drum at the appropriate flow rate. In instances where the additive is admixed with the coker feedstock prior to its injection into the coker drum, it may be necessary to employ a small amount of a mutual solvent. For example, if the gas, liquid or solid additive is not sufficiently soluble in the coker oil feed, it is preferred to employ between about 0.1 and weight percent of a mutual solvent along with the coker feed to increase the solubility of the additive in the feed; however, the mutual solvent is not essential since the halogen compound can also be dispersed or suspended in the coker oil feed.

Many mutual solvents may be employed in accordance with this invention and can generally comprise any liquid organic solvent which has sufficient solvency for the halogen,

7 hydrogen halide or hydrocarbyl halide additive and for the emplary solvents include aliphatic, alicyclic or aromatic compounds or esters, acids, amines, amides, alcohols, ketones, aldehydes, or ethers thereof having from two to about 12 carbon atoms. Exemplary aliphatic hydrocarbons include propane, butane, pentane, octane, pentene, octene, etc.; alicyclic hydrocarbons such as cyclobutane, cyclohexane, methyl cyclohexane, propyl cyclohexane, etc.; aromatic hydrocar- 5 bons such as benzene, methyl benzene, toluene, etc.; esters such as methyl acetate, ethyl acetate, n-propylpropionate, isopropyl acetate, isoamyl acetate, n-amyl acetate, furfural acetate, isoamyl n-butyrate, isoamyl propionate, benzyl acetate, etc.; alcohols such as propanol, isopropanol, butanol, isobutanol, heptanol, propylene glycol, benzyl alcohol, cyclohexanol, isoheptanol, etc.; ethers such as methyl ethyl ether, diethyl ether, diisopropyl ether, dioxane, diisoamyl ether, ethyl heptyl ether, isobutylamyl ether, diphenyl ether, methylphenyl ether, etc.; carboxylic acid such as acetic acid, propanoic acid, isopropanoic acid, butanoic acid, pentanoic acid, hexanoic acid, benzoic acid, etc.; ketones such as ethylmethyl ketone, ethylethyl ketone, ethyl isopropyl ketone, amyl isopropyl ketone, ethylbenzyl ketone, etc.; amides such as N-methyl formamide, N,N-dimethyl fonnamide, N-ethyl formamide, N,N-diisopropyl formamide, N-benzyl formamide, etc.; and amines such as ethylamine, dimethylamine, triethylamine, isopropylamine, isobutylamine, benzylarnine isocetylamine, etc. 7 W 7 WW V The amount of halogen, hydrogen halide or hydrocarbyl halide which can be introduced into the coking unit to effectively improve the coke volatile combustible material unifonnity can vary over a wide range depending upon the operating con ditions of the coking drums. Generally, any amount less than 0.1 weight percent can be employed; however, it is preferred that the amount of additive be maintained between about 0.001 and 0.05 weight percent, and preferably between about 0.002 and 0.02 weight percent of the coker feedstock.

According to the process of this invention, a high boiling hydrocarbon feed is preheated to a coking temperature, generally between about 800 and l200 F., preferably between about 850 and 950 F., and most preferably between about 935 and 950 F. Typical coker feeds include virgin crude, bottoms from the vacuum distillation of reduced crude, thermal tar, Due-Sol extract, furfural extract, vacuum tar, reduced crude, topped crude and blends thereof. High aromatic content feedstocks are well suited for coking since they yield a coke that can be processed into a quality graphite. Examples of such feedstocks are the refractory cycle stocks obtained from thermal and catalytic cracking processes and boiling in the gas oil range. Decant oil from fluid catalytic cracking is another example of such high aromatic content feedstocks. The preheated feedstock is then fed into the bottom of the delayed coker drum along with an effective amount of the halogen, hydrogen halide or hydrocarbyl halide additive. The coking feed is allowed to soak in its own heat in the delayed coker at a low pressure, generally between about 1 and 10 atmospheres absolute, preferably between about 2 and 7 atmospheres. The cracked vapors are continuously removed overhead so as to recover the distillate fuels, while coke is allowed to build up to successively higher levels in the drum. The amount of additive introduced into the coker drum is preferably increased as the coke builds up in the drum so that a constant amount of halogen, hydrogen halide or hydrocarbyl halide can be maintained at the uppermost level of the coke or liquid residue undergoing coking in the drum. Generally, the amount of the additive is increased by 0.0001 to 0.0005 weight percent for each vertical foot of coke in the coker drum. When the drum is tilled with coke, the preheated feed is diverted to a succeeding drum, and the former drum is steamed out and cooled. The coke is then removed from the cooled drum by conventional means.

The coke recovered from the coker drums of this invention have been found to possess a relatively uniform volatile combustible material content which generally varies over a range of about 6 weight percent. In many cases, however, the volatile combustible material content uniformity is maintained within a range of about 4 weight percent. Thus the introduction of a halogen, hydrogen halide or hydrocarbyl halide to a conventional coking feed, results in a coke product having a volatile combustible material content between about 9 and 15 weight percent and in many coking processes the recovered coke has a volatile combustible material content between about 10 and 14 weight percent.

The following examples are cited to illustrate the results obtainable in the practice of one specific embodiment of this invention, but it not to be construed as limiting the scope of the invention as defined by the appending claims.

Example I This example illustrates the effectiveness of the halogen containing compounds in improving the coke uniformity. A reduced crude oil for a Colorado field having the properties set forth in table 1 is preheated to 900 inside and charged into two experimental coker drums, A and B, which are cylindrical chambers having a 4-inch inside diameter and a 30-inch height. The coker feed throughput is maintained at a sufficient flow rate so that both drums can be filled to 18 inches in a 4- hour period. The vapors released by the coking feed are withdrawn overhead from the experimental drums.

A small amount of liquid ethylene bromide is admixed with the coker feed injected into coker drum B while no additive is admixed with the feed to drum A. Initially, 0.005 weight percent of the bromide is introduced into the feed and after 2 hours -of operation the amount of ethylene bromide is increased to 0.008 weight percent of the coker feed.

At the end of the delayed coking run, the coke from each drum is analyzed at various drum heights to determine the volatile combustible material content. The results from this test are shown in table 2 and also by the attached drawing.

TABLE 1 Coker Feed-Colorado Reduced Crude Volatile Combustible Material as determined by ASTM D-27 l-48 It is clearly apparent from the above table that the addition of the ethylene bromide to the coking drum improved the volatile combustible material uniformity in the coke from a percentage span of 14 weight percent to a more uniform span of 4.5 weight percent EXAMPLE 2 To illustrate the practice of this invention with a halogen, molecular bromine is bubbled through a mixture of Colorado reduced crude as employed in example l and about 5 weight percent of acetic acid. The bromine is injected into the mixture until approximately 0.005 weight percent of the bromine is absorbed into the feedstock mixture. The mixture is then subjected to delayed coking in substantially the same manner as described in example 1.

EXAMPLE 3 Tln this example, 0.008 weight percent of solid 2,6 dichloronaphthalene is dissolved in a Colorado crude as employed in example 1. The mixture is heated to 900 F. and subjected to delayed coking in substantially the same manner as described in example 1. Although I have described the present invention in connection with specific embodiments thereof, it is not intended that the details set forth shall be regarded as limitation upon the scope of the invention, except insofar as indicated in the following claims.

I claim: 1. In the method of making improved coke wherein a hydrocarbon coking oil feed is preheated and charged into a delayed coking drum at conditions comprising a temperature from 800 to l200 F. and a pressure from 1 to 10 atmospheres, sufficient to reduce said feed to dry coke vapors, the improvement comprising introducing into said coking drum a halogen, hydrogen halide or hydrocarbyl halide having from two to 20 carbon atoms in an amount effective to improve the coke uniformity.

2. The method defined in claim 1 wherein said hydrocarbon coking oil feed comprises a crude oil residuum 3. The method defined in claim 1 wherein said hydrocarbyl halide is selected from the group consisting of aliphatic halides having from one to about 20 carbon atoms, alicyclic halides having from three to about 20 carbon atoms, and aromatic halides having from six to about 20 carbon atoms.

4. The method defined in claim 3 wherein said hydrocarbyl halide is hydrocarbyl bromide.

5. The method defined in claim 1 wherein said halogen, hydrogen halide or hydrocarbyl halide is injected into said coking drum in an amount of'between about 0.001 and 0.2 weight percent of said coking oil feed.

6. The method defined in claim 5 wherein the amount of halogen, hydrogen halide or hydrocarbyl halide injected into said coking drum is increased as the amount of coke within the coking drum increases.

7. A process for making an improved delayed coke composition which comprises:

preheating a high boiling hydrocarbon coker feedstock to a temperature between about 800 to about 1200 F.;

injecting a halogen, hydrogen halide or hydrocarbyl halide having from one to about 20 carbon atoms into said feed in an amount between about 0.002 and 0.2 weight percent of said feedstock;

thereafter charging the mixture into a delayed coking drum at conditions conductive for delayed coking; continuously removing product vapors from said coking drum; and

allowing an appreciable amount of coke to form within said coking drum.

8. The method defined in claim 7 wherein said hydrocarbyl halide is selected from the group consisting of aliphatic halides having from one to about 20 carbon atoms, alicyclic halides having from three to 20 carbon atoms, and aromatic halides having from six to about 20 carbon atoms.

9. The method defined in claim 8 wherein said hydrocarbyl halide is a hydrocarbyl bromide.

10. The method defined in claim 9 wherein the amount of hydrocarbyl bromide injected into said coking drum is increased during coking. 

2. The method defined in claim 1 wherein said hydrocarbon coking oil feed comprises a crude oil residuum.
 3. The method defined in claim 1 wherein said hydrocarbyl halide is selected from the group consisting of aliphatic halides having from one to about 20 carbon atoms, alicyclic halides having from three to about 20 carbon atoms, and aromatic halides having from six to about 20 carbon atoms.
 4. The method defined in claim 3 wherein said hydrocarbyl halide is hydrocarbyl bromide.
 5. The mEthod defined in claim 1 wherein said halogen, hydrogen halide or hydrocarbyl halide is injected into said coking drum in an amount of between about 0.001 and 0.2 weight percent of said coking oil feed.
 6. The method defined in claim 5 wherein the amount of halogen, hydrogen halide or hydrocarbyl halide injected into said coking drum is increased as the amount of coke within the coking drum increases.
 7. A process for making an improved delayed coke composition which comprises: preheating a high boiling hydrocarbon coker feedstock to a temperature between about 800* to about 1200* F.; injecting a halogen, hydrogen halide or hydrocarbyl halide having from one to about 20 carbon atoms into said feed in an amount between about 0.002 and 0.2 weight percent of said feedstock; thereafter charging the mixture into a delayed coking drum at conditions conducive for delayed coking; continuously removing product vapors from said coking drum; and allowing an appreciable amount of coke to form within said coking drum.
 8. The method defined in claim 7 wherein said hydrocarbyl halide is selected from the group consisting of aliphatic halides having from one to about 20 carbon atoms, alicyclic halides having from three to 20 carbon atoms, and aromatic halides having from six to about 20 carbon atoms.
 9. The method defined in claim 8 wherein said hydrocarbyl halide is a hydrocarbyl bromide.
 10. The method defined in claim 9 wherein the amount of hydrocarbyl bromide injected into said coking drum is increased during coking. 